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In a year that the price of oil has fallen to levels not seen since 2009, it seems ironic that a number of yacht-builders have been unveiling plans for more efficient vessels. Marinas, too, have been responding to ever more demanding environmental requirements.

Leading the field this year in greener superyachts is the 83.5m Savannah, launched in March by Feadship Royal Dutch Shipyards, that claims fuel economies of up to 30 per cent in using a single Wärtsilä diesel engine alongside three generators, batteries, propeller, azimuth thruster pod (marine propellers placed in pods that can be rotated to any horizontal angle) and a streamlined hull.

Savannah, built by Feadship’s Royal de Vries yard, is a pioneer in what a number of yards hope will become the next generation of superyachts.

But to do that, builders and designers must convince clients that greener sailing is an attractive proposition. Diesel-electric hybrid yachts are not new. The Lürssen-built Limitless, launched in 1997, was the first. Today, Lürssen has detailed plans for a yacht that runs on liquefied natural gas.

“I’m convinced we will see a yacht with LNG sooner rather than later,” said Peter Lürssen, the company’s chief executive, speaking in London earlier this year at the Top 100 event organised by Superyachts.com and Y.CO, the broker.

In the meantime, the company has focused on greening its shipyard, spending €2m on industrial filters and extractors to improve the construction process.

“We can push a yacht through the water at 50 per cent of the cost of what it was 10 years ago, and at the same speed, because of continuous optimisation of efficiencies and energy management,” said Mr Lürssen.

One of the yard’s most progressive innovations has been what it calls “peak shaving”, which reduces the demands upon its generators by allowing battery power to cut in during periods of maximum output. The system is more fuel-efficient than running generators at capacity.

The Italian builder Viareggio Super Yachts first introduced dynamic positioning systems to its boats — these keep vessel in specified position limits to minimise fuel consumption and wear and tear of propulsion equipment. It has now appointed a sustainability manager, Vienna Eleuteri, charged with improving environmental conditions and delivering what she calls a “born to be green” workshop. The yard has already reduced carbon dioxide emissions by 20 per cent in the life-cycle of its yachts, and believes it can reduce them still further.

Oceanco is the Dutch yard that built Equanimity (one of the stars of the 2014 Monaco Yacht Show); green production now underpins its operations.

“Looking at different, more efficient propulsion systems and reducing emissions is an absolute given,” says Marcel Onkenhout, Oceanco’s CEO. The yard is currently building Project Solar, set to be the world’s largest sailing yacht at 106m; it has a DynaRig system (a square rig twice as efficient as conventional ones) that, in addition to wind, will rely heavily on solar power for its energy systems.

Hybrid systems on yachts, like those in cars, tend to cost more than conventional power units. And while such systems do deliver efficiencies, hull design and streamlining tend to make a bigger difference.

Even more important is the way that owners use their yachts and their choice of cruising speeds. “There is an exponential curve in power output needed to deliver speeds upwards of 15 knots,” says Andreas Iseli, head of exterior design at Andrew Winch Designs.

“We had a two-engined boat that would cruise at 17 or 18 knots and could reach a speed of 21 to 22 knots,” he says, “but the client wanted a top speed of 24 knots. To deliver that extra two knots, we had to double the number of engines to four.”

Just as in a domestic house efficiencies can be delivered by owners, but most have their yachts in what the industry calls “hotel mode” — running air-conditioning, audiovisuals, a mass of lighting, plus refrigeration units, freezers and all the on-board electronics.

A superyacht is “always on” and always crewed, argues Martin Bellamy, chairman and chief executive of Salamanca Group. The group has invested $100m in a 146-berth marina in Barcelona under its OneOcean brand that has won a number of environmental awards.

“Everyone in this industry today has to be conscious of the environment and we have incorporated working practices — such as energy-efficiency and waste management — into all aspects of our marina. For example, the OneOcean Gallery (the marina’s reception) is wrapped in environmentally friendly concrete that adapts to the changing seasons.”

In Dubai, the shipping logistics company GAC, is operating a suction scrubbing device called HullWiper which ensures that crusted deposits on ships’ hulls are sucked into containers and disposed of on land, instead of dropping to the seabed. The company has taken the system into Europe and Asia, and believes it has strong potential in the superyacht sector.

Even sail power, sometimes regarded as the greenest of energy, has its drawbacks if big yachts are racing with expensive carbon sails. The cost of maintaining a set of competitive sails can outweigh engine-running costs, depending on how frequently sails are changed.

This, however, has not deterred designers, yards and marinas from trying to persuade buyers to be more environmentally aware. In some cases, changes are forced upon builders through legislation. Most yards today are future-proofing their engine-room builds, for example, ahead of expected new regulations on engine-room size and exhaust filtration planned by the International Maritime Organization.

In Monaco today another Dutch yard, Heesen, is unveiling its latest 50m build project. Nova combines a fast displacement design, pioneered on yachts such as Galactica Star, with a hybrid propulsion system that engages diesel engines and electric generators to deliver more efficient power distribution and fuel savings akin to those on Savannah.

But the marketing of Nova is focused as much on the silence of its propulsion system as on its fuel savings. “At slow speeds, you can operate the yacht without the use of the engines. The generator-fed electric motors alone can power the yacht up to 9 knots. This makes it incredibly silent,” says Mark Cavendish, Heesen’s head of sales and marketing.”